Microbial dechlorination of HCB, PCP, PCB180, HCH and PCE in a Yangtze Three Gorges Reservoir enrichment culture, China

Highly chlorinated pollutants are often found in river sediments, such as in the Yangtze River. In this study, the transformation of hexachlorobenzene, pentachlorophenol, polychlorinated biphenyl (PCB), hexachlorocyclohexane and perchloroethene was demonstrated in a mixed microbial culture enriched from Xiangxi River sediment [a tributary of Yangtze River belonging to the Three Gorges Reservoir (TGR)] which contained halo-respiring bacteria. Reductive dehalogenation by the Yangtze bacteria resulted in the formation of lower chlorinated metabolites, such as tri- and dichlorobenzenes, tri- and dichlorophenols, vinyl chloride and ethene. In case of PCB180, the lesser chlorinated metabolite PCB146 was detected and is recommended for future monitoring programs. Increased gene copy numbers of dechlorinating bacteria, e.g. Dehalococcoides spp. and Desulfitobacterium spp., were observed after the transformation of the chlorinated pollutants. In conclusion, the study demonstrates the capability of Yangtze River bacteria to dechlorinate several important chlorinated pollutants, indicating efficient pollutant turnover in the TGR area.